1. Technical Field
This disclosure relates to voltage supply control and, more particularly, to control mechanisms for voltage supplies of microprocessors.
2. Description of the Related Art
Computer system processors typically require precise voltages during operation. Accordingly, these computer systems typically employ tightly controlled voltage regulators with multiple voltage settings. The voltage settings are generally selected through the use of voltage identification (VID) signals. One mechanism to obtain tight control over the output voltage is to use some form of load line compensation. In many systems, for each output voltage, a particular load line may be used that defines a voltage range within which the output voltage may vary as the load current varies from a minimum up to a maximum current for the given voltage setting. More particularly, load line voltage ranges may be tuned such that as the load current increases up to the maximum, the output voltage may be reduced from a maximum voltage to a minimum voltage for that voltage setting. This type of load line may take advantage of the fact that exposure to frequency-impacting voltage droops is lower at high load conditions than at low load conditions. Thus, the output voltage may be lower at maximum current which may reduce the power consumption.
However, there are some drawbacks to such load line compensated regulators. For example, to reduce the exposure to (i.e., a voltage droop caused by) sudden increases in load current, when the load currents are low, the load line dictates that the output voltage be increased to some suitable voltage that will reduce the exposure. Thus although this type of load line compensation may be an appropriate control mechanism for moderate to heavy loads, lightly loaded regulators may consume more power than is necessary due to the higher supply voltage. This may be especially undesirable in battery-operated systems or any system concerned with power savings.